1. Field of the Invention
The present invention relates to recording thin-film magnetic heads used, for example, in floating type magnetic heads. More particularly, the present invention relates to a thin-film magnetic head generating leakage flux at a satisfactory location in the vicinity of a gap layer so as to fulfill the requirements for high recording density and high recording frequency, and relates to a manufacturing method therefor.
2. Description of the Related Art
FIG. 31 is a partial front view showing the structure of a conventional thin-film magnetic head (inductive head), FIG. 32 is a partial cross-sectional view of the thin-film magnetic head taken along the line 32—32 in FIG. 31 and observed from the direction indicated by the arrow shown therein.
Reference numeral 1 in FIGS. 31 and 32 indicates a lower core layer composed of a magnetic material such as a permalloy, and an insulating layer 9 is formed on the lower core layer 1.
A groove 9a extending from an opposing face (hereinafter referred to as the ABS surface) opposing a recording medium in a height direction (the Y direction in the figure) is formed in the insulating layer 9, and the inside width of the groove 9a is equivalent to a track width Tw.
In the groove 9a, a lower magnetic layer 3 magnetically coupled with the lower core layer 1, a gap layer 4, and an upper magnetic layer 5 magnetically coupled with an upper core layer 6 are sequentially formed from the bottom by plating.
As shown in FIG. 31, the upper core layer 6 is formed on the upper magnetic layer 5 by plating.
As shown in FIG. 32, a coil layer 7 patterned in the spiral form is formed on the insulating layer 9 at a place extending from the groove 9a formed in the insulating layer 9 in the height direction (the Y direction in the figure).
The coil layer 7 is covered with a coil insulating layer 8 composed of a resist or the like, and the upper core layer 6 is formed on the coil insulating layer 8. The upper core layer 6 is magnetically coupled with the upper magnetic layer 5 at a front portion thereof and is magnetically coupled with the lower core layer 1 at a base portion 6b of the upper core layer 6.
In the inductive head shown in FIGS. 31 and 32, when a write current is applied to the coil layer 7, a recording magnetic field is induced in the lower core layer 1 and the upper core layer 6, so that a magnetic signal is written on a recording medium such as a hard disk by a magnetic field leakage generated from a gap between the lower magnetic layer 3 magnetically coupled with the lower core layer 1 and the upper magnetic layer 5 magnetically coupled with the upper core layer 6.
In the inductive head shown in FIGS. 31 and 32, in the vicinity of the ABS surface (the face opposing a recording medium), the lower magnetic layer 3, the gap layer 4, and the upper magnetic layer 5, having widths equivalent to the track width in some parts thereof are formed, whereby the inductive head mentioned above can be applied to a narrower track width configuration.
A method for manufacturing the inductive head shown in FIGS. 31 and 32 will be described. The insulating layer 9 is formed on the lower core layer 1, and the groove 9a having the width equivalent to the track width Tw and a predetermined length extending from the ABS surface in the height direction is formed in the insulating layer 9.
Next, in the groove 9a, the lower magnetic layer 3, the gap layer 4 and the upper magnetic layer 5 are sequentially formed by plating, and the coil layer 7 having a pattern is subsequently formed on the insulating layer 9 in a posterior region (in the height direction) of the groove 9a formed in the insulating layer 9.
In addition, the coil insulating layer 8 is formed so as to cover the coil layer 7, and the upper core layer 5 is continuously formed on the upper magnetic layer 5 and the coil insulating layer 8 by flame plating, whereby the inductive head shown in FIGS. 31 and 32 is completed.
In the thin-film magnetic head shown in FIGS. 31 and 32, as described above, when a write current is applied to the coil layer 7, a recording magnetic field is induced in the lower core layer 1 and the upper core layer 6, and magnetic flux flows into the lower magnetic layer 3 and the upper magnetic layer 5.
However, as shown in FIG. 32, lengths T1 of the lower magnetic layer 3, the gap layer 4, and the upper magnetic layer 5 extending from the ABS surface to the back ends thereof in the height direction are equal to each other.
The length T1 is called a gap depth (Gd), and in conventional thin-film magnetic heads, the length of T1 must be very short in order to increase the leakage flux from the gap layer 4.
However, in the thin-film magnetic head shown in FIG. 32, as described above, since the lengths T1 of the lower magnetic layer 3, the gap layer 4, and the upper magnetic layer 5 extending from the ABS surface to the back ends thereof in the height direction are formed to be equal to each other, when the T1 is formed to be shorter, an area of an interface between the upper core layer 6 and the upper magnetic layer 5 is accordingly smaller. Consequently, the magnetic flux flowing into the upper core layer 6 is restricted at the interface mentioned above, and the magnetic flux is in a state of magnetic saturation before reaching the gap layer 4. That is, leakage flux is generated at a location other than the vicinity of the gap layer 4, and particularly when recording frequency is increased, there is a problem in that accurate recording cannot be performed.
In the thin-film magnetic head shown in FIGS. 31 and 32, in order to suppress the generation of write fringing, a distance H1 in the vicinity of the ABS surface from the upper surface of the lower core layer 1 to the bottom surface of the upper core layer 6 must be larger.
However, when the distance H1 is larger, the magnetic flux is more likely to be in a state of magnetic saturation before reaching the gap layer 4. As has thus been described, the structure of the conventional thin-film magnetic head cannot have superior magnetic flux flow while suppressing the generation of write fringing.